(Reuters) - Roche has bought the rights to an experimental drug from Spain's Oryzon Genomics that can switch on genes to block cancer growth, as the Swiss drugmaker looks to maintain its dominance in the lucrative field of oncology.

The world's largest maker of cancer drugs will pay Barcelona-based Oryzon $21 million in upfront and near-term milestone payments and could pay out more than $500 million if the company meets other goals, it said in a statement on Monday.